Welcome to Apnea Board ! As a guest, you are limited to certain areas of the board and there are some features you can't use. To post a message, you must create a free account using a valid email address.
Login or Create an Account

This post is my personal observation from using my new APAP for about 2 months.
It is an experiment I did regarding "lowest effective pressure" and the sufficiency of controlling AHI and SO2 for best OSA therapy (for standard OSA)

SYNOPSIS: lowest effective pressure based on AHI is not sufficient therapy.

DETAILS:
My recent sleep study reported that 14cmH2O was my designated pressure and that pressure support was required so I got a bilevel. (this test is suspect because I cannot sleep during lab tests) I requested an auto PAP and my doctor complied. She called for an IPAP range of 10-18 which she achieved by calling out the necessary min EPAP and PS.

This machine, with minor setting adjustments on my part (PS) did a significantly better job at improving my sleep than my old CPAP machine which I had previously been using for years and which ran at a pressure setting of 8cmH2O, EPR on 3, and no data availability. My new machine settled at a 95% pressure of 10.5cm. (10 is the min IPAP allowed by the settings).

So I have been very curious about what my breathing was doing on the old machine. I thought it was working well as it allowed me to sleep much better than before CPAP. But, in hindsight, I had nocturia and occasional light nighttime headache and woke up frequently during the night. I am aware of that now because I don't have those symptoms any more.

I decided to set my new machine at the old setting and collect some data.
So I set the APAP to begin at a min EPAP of 5 with a PS of 3, giving me my 8cm pressure point and let it run in auto mode.

The results were very interesting to me. First of all I did not sleep well compared to the last 2 months. I woke up a lot, had to get up to use the bathroom, and I had a night time headache. I felt bad in the morning.
The data for this night showed lots of low level flow limits, the pressure adjust was quite active but stayed below 9.6. I had one CA over the entire night and there were no other apneas of any duration. There was however, a lot of rough breathing and all of my flow data was funky looking, narrow and pointy rather than smooth and rounded.
Anyone looking at the statistics would think this was a great therapy night and that running at a lower pressure of 8 cm was the way to go compared to the statistics for the 10.5 cm runs which are similar. Not so. I think my body and my sleep feel the effects of the increased struggle to breath even if the statistics don't show it. I would have no problem with SO2 on the lower setting as was the case with my old machine but I was was not getting restful sleep. I suspect that if I let the auto run from an IPAP of 4cm (PS=0) I would end up with an even lower 95% pressure than 8. I won't test that because I don't want to suffer the bad night it would cause.

Makes me think about increasing the min EPAP setting another notch on my new machine just to check.......

There is some confusing information in your post. You seem to be using a BPAP (bilevel) Auto machine. So when you say,

Quote:So I set the APAP to begin at a min EPAP of 5 with a PS of 3, giving me my 8cm pressure point and let it run in auto mode.

This sounds like an APAP machine.

The EPAP on a bilevel machine needs to be high enough to resolve all OSA. Remaining H and RERA can be addressed with pressure support. A min EPAP of 5.0 and PS min of 3.0 gives you 5.0/8.0 IPAP/EPAP which is clearly well below your prescribed pressures. It appears you need an EPAP closer to 7.0 and a PS of 4 to be closer to prescription. This would give you 7/11 pressure minimum, and I presume you'd allow the max IPAP to go to 18 as needed.

(07-08-2015, 11:01 AM)MobileBasset Wrote: It is an experiment I did regarding "lowest effective pressure" and the sufficiency of controlling AHI and SO2 for best OSA therapy (for standard OSA)

Why are you trying to control your sulfur dioxide??? I knew what it meant but it struck me funny (yes I am weird).

Sleeprider,

OP is using a Bilevel Auto machine in Vauto mode, I believe.

MobileBasset,

I think that I see what you re doing but am somewhat confused. You are apparently running in Vauto mode, so you are setting min EPAP and PS but I see no mention of your setting of max IPAP. are you setting max IPAP or are you just leaving it wide open?

(07-08-2015, 11:40 AM)Sleeprider Wrote: There is some confusing information in your post. You seem to be using a BPAP (bilevel) Auto machine. So when you say,

Quote:So I set the APAP to begin at a min EPAP of 5 with a PS of 3, giving me my 8cm pressure point and let it run in auto mode.

This sounds like an APAP machine.

The EPAP on a bilevel machine needs to be high enough to resolve all OSA. Remaining H and RERA can be addressed with pressure support. A min EPAP of 5.0 and PS min of 3.0 gives you 5.0/8.0 IPAP/EPAP which is clearly well below your prescribed pressures. It appears you need an EPAP closer to 7.0 and a PS of 4 to be closer to prescription. This would give you 7/11 pressure minimum, and I presume you'd allow the max IPAP to go to 18 as needed.

Yes, my new machine is an auto Bilevel as you can see in my profile. The prescription was set on it as the doctor prescribed but the autoset settled on the low end of the prescription range. It is set to a min EPAP of 6cm, PS=4 (ResMed, so PS does not vary) and max IPAP=18. I don't discuss the max IPAP because it is too high to effect anything. I will lower this eventually. So it runs in auto and settles mostly at EPAP 6.6 and IPAP 10.6. It seems to be working well for me.

For the experiment I lowered everything to be like my previous machine, which was a straight CPAP running at 8 with EPR=3. I set min EPAP=5, PS=3' max IPAP still at 18. I ran in auto mode. The lower(below current prescription) pressure is what I had been using for years, it was my previous prescription and I thought it was working while I was using it. The experiment was trying to recreate my old machine operation and collect data. I wanted to find out what level of therapy I had been receiving with it for all those years at that lower pressure level. (The old machine had no detailed data). I also wanted to find what the autoset would do to the starting pressure of 8.

I found out it didn't do much. Because there were no OSA, no H and few RERA to respond to. But there was enough labored breathing to make me loose sleep. It did not respond to that.

(07-08-2015, 11:01 AM)MobileBasset Wrote: It is an experiment I did regarding "lowest effective pressure" and the sufficiency of controlling AHI and SO2 for best OSA therapy (for standard OSA)

Why are you trying to control your sulfur dioxide??? I knew what it meant but it struck me funny (yes I am weird).

Sleeprider,

OP is using a Bilevel Auto machine in Vauto mode, I believe.

MobileBasset,

I think that I see what you re doing but am somewhat confused. You are apparently running in Vauto mode, so you are setting min EPAP and PS but I see no mention of your setting of max IPAP. are you setting max IPAP or are you just leaving it wide open?

Best Regards,

PaytonA

Ha ha, not a good abbreviation for oxygen saturation, thanks.

My max IPAP is set at 18 as prescribed. I did not change that. My pressure has never gone above 11.6. When I am all done fooling around I will tighten that up.

Additional note.
If I was getting valid sleep lab data it would be shown in the EEG data when I was getting restful sleep and when I was not, so hopefully that would be taken into account along with the apnea events and O2 saturation to provide the optimum prescribed PAP settings. And those settings would be higher than ones that merely controlled events. If I reviewed the data with my doctor and was convinced the lab data was valid I would definitely be content with that prescription.
However, my sleep tests are always a circus. So they end up SWAGing the script.

I agree, to a point. AHI is very dumbed-down and does not tell us much; it is very handy and useful for what it is, obviously totally useless for what it is not. 02 is important, but not the whole story.

That said, I think the "lowest effective pressure" concept is very pertinent when applied to classic OSA, and much more than it would be applied to conditions that would result in Bi-PAP or ASV, ventilators, etc. That is indeed more complex, and "lowest effective pressure" is not even close to being all that is needed.

A very interesting experiment. Proves some of the key points I have gathered in my research in this:
1) Suboptimal PAP therapy is still superior to no therapy.
2) AHI is at best a proxy variable for what is the primary objective which is to keep so2 levels good AND maintain/promote good sleep architecture.

Sometimes, while you are on your way to an event, you wake up a little, have a RERA to keep your SO2 high. It doesn't register as an event for AHI calc but it still disturbs the sleep architecture. People need more pressure typically to stave off RERAs. It also reduces AHI and thus a lot of people swear by reducing AHI to less than 1.

For some people, You need higher pressure support to promote co2 washout and result in higher so2. You may be one of them.

I agree, to a point. AHI is very dumbed-down and does not tell us much; it is very handy and useful for what it is, obviously totally useless for what it is not. 02 is important, but not the whole story.

That said, I think the "lowest effective pressure" concept is very pertinent when applied to classic OSA, and much more than it would be applied to conditions that would result in Bi-PAP or ASV, ventilators, etc. That is indeed more complex, and "lowest effective pressure" is not even close to being all that is needed.

As an aside, and only taking into consideration CPAP lab titration and Sp02 sats/desats for purposes of my comment, my 'lowest effective pressure' would have been 7cm with and RDI of 3.3. But due to low sats/desats at lab titration, optimal pressure was 12cm before lowest Sp02 exceeded 90%. That is quite an increase.

Unfortunately, non-sleep doc prescribed auto at 6-15cm, and it resulted in average pressures of only 6 or 7cm with fine AHI's. But there is little doubt I was hypoxic at those low average pressures. I took it upon myself to conduct my own overnight oximeter studies and also saw a pulmonologist who suggested raise in pressure to 9-15cm for other reasons related to REM observed at 9 in study. What seems to overall work best for me now is straight CPAP at 11.5cm. There it is, and it's not taking into consideration other factors. I have it down pretty well, because to my knowledge I do not have complicating factors that might render BPAP or ASV appropriate.

Useful Links

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.